Such antennas, particularly omnidirectional transmitting antennas that are to be embedded or lowered, if they should have a substantial power, they are all the heavier and bulkier, the lower their emitting frequency.
To lighten the construction of such antennas, there are known omnidirectional piezoelectric transducers that are constituted by cylindrical envelopes having at their interiors regularly and evenly distributed radial piezoelectric drivers without any mechanical connection among themselves except the envelopes. One knows that such transducers present two principal resonant frequencies of which one is less than to the inherent or fundamental frequency of the envelope, which arrangement allows one to obtain lower frequencies for the same weight and space requirement.